The present invention relates to treatment with ozone, especially of a fluid, especially of waters to be made drinkable.
The conventional ozonisation processes comprise the injection under pressure of a gas containing ozone into a treatment reactor or vessel containing, for example, the fluid to be treated, the undissolved gases being recovered at the column vents, and expelled to atmosphere after optional destruction of the ozone, or are recycled.
These processes are, for example, used conventionally with a diffusion system of bubble column type having porous diffusers. The flowrate of the injected gas leads to homogenisation of the concentrations of dissolved gas.
There is additionally known a process in which recycling of the gas is carried out between the outlet of a contactor and the inlet of the ozoniser, in order to limit operating costs. After destruction of the ozone contained in the air and then desiccation, the gas is conveyed to the ozoniser where fresh oxygen is introduced.
One disadvantage of this process is that the gas forced back at the reactor vents does not contain solely oxygen and ozone but also, among others, nitrogen and water. The problem which was then posed was the necessity of working at a high oxygen concentration; this then involved not insignificant purge flowrates. These purge flowrates depend on the gases absorbed or desorbed at the reactor outlet.
U.S. Pat. No. 4,352,740 describes a process for ozonising a flow of water in which a gas containing at least 70% of oxygen is conveyed into the ozoniser, generating an ozone content of the order of 4 to 8%, the gas thus obtained is then injected into the waste waters and the ozone-poor gas is released to atmosphere at the outlet of the reactor for treating the flow of water, after passing through an ozone destroyer.
As a result of the high concentration of oxygen and ozone in the gas at the inlet of the reactor for treating water, the disadvantage of this process consists in that the flowrate of ozonisation gas is very low with respect to the flowrate of the fluid to be treated, which does not make it possible to obtain homogeneous diffusion of the ozonisation gas in the fluid to be treated, and thus good mixing of the fluid and the gas, in particular when conventional columns for the ozonisation of water, of bubble column type, are used, and for this reason does not make it possible to carry out an optimised treatment of the fluid.